1. Field of the Invention
The present invention relates to a head carriage device of a floppy disc drive used as an external memory device and the like of a computer.
2. Description of the Related Art
FIG. 9 and FIG. 10 are a plan view and a side view, respectively, of a head carriage device 1. FIG. 11 is a front view, in a direction E, of the head carriage device 1 shown in FIG. 9.
As shown in FIGS. 9 and 10, the head carriage device 1 includes a carriage 2, which is held movably in a radial direction of a floppy disc 9 (in a direction R in the drawings) and which is provided with a magnetic head 5. The head carriage device 1 also includes a head arm 3 having a magnetic head 6 opposing the magnetic head 5, a flat spring 4 extending from an end 3b of the head arm 3, and a fixing member 11 connecting the flat spring 4 to the carriage 2. The fixing member 11 overlaps a free end of the flat spring 4. The head carriage device 1 further includes a torsion spring 7 resiliently urging the magnetic head 6 toward the magnetic head 5 at an anchoring point 3c provided at the central part in the width direction (in a direction shown by arrows W in FIG. 9) of the head arm 3, and a finger 3a supported by a lifting mechanism 8 and protruding toward the outside from one of the sides along the direction R of the head arm 3, for pivoting the head arm 3 in direction increasing the spacing between the magnetic head 6 and the magnetic head 5 (direction A in FIG. 10).
The head carriage device 1 operates as follows. When a cartridge 10 holding a floppy disc 9 is inserted in a floppy disc drive (not shown), as shown in FIG. 11, the lifting mechanism 8 is applied to the finger 3a. The magnetic head 6 moves in the direction A (unloading direction) while being supported through the finger 3a, as shown in FIG. 10. The lifting mechanism 8 forces the distance between the magnetic head 6 and the magnetic head 5 to increase, against the resilient force of the torsion spring 7.
When the cartridge 10 is completely inserted in the floppy disc drive, the lifting mechanism 8 releases the unloaded state of the head arm 3. The head arm 3 then moves in a direction B (loading direction), as shown in FIG. 10, in which the magnetic head 6 approaches the magnetic head 5, and the magnetic heads 5 and 6 clamp the floppy disc 9 with a predetermined pressing force. The pressing force is determined by the torsion spring 7. The floppy disc 6 is subsequently driven by a spindle motor (not shown) and reading/writing of information is performed by the magnetic heads 5 and 6.
However, in the head carriage device 1, in which the head arm 3 turns while being supported at one side of the head arm 3, it is possible for the magnetic head 6 to interfere with the cartridge 10 at an end 6a of the magnetic head 6 when inserting the cartridge 10 in the floppy disc drive. This interference occurs due to the structure of the head carriage device 1. Because the head arm 3 is fixed to the carriage 2 through the fixing member 11 at the free end of the flat spring 4 extending from the end 3b of the head arm 3, when the head arm 3 turns along the direction A shown in FIG. 10, the head arm 3 is inclined from a horizontal line H shown in FIG. 11. Thus, the distance between the magnetic head 6 mounted on the head arm 3 and the magnetic head 5 is larger at an end 6b of the magnetic head 6 at the side of the finger 3a than the distance at the opposing end 6a of the magnetic head 6. A torque D, shown in FIG. 11, causes the inclination of the head arm 3. The torque D is produced because an anchoring point C of the finger 3a, to which the lifting mechanism 8 is applied, is disposed at a distance from the anchoring point 3c of the head arm 3 to which a pressing force F of the torsion spring 7 is applied.
Another head carriage device 20, shown in FIGS. 12 and 13, is disclosed in Japanese Unexamined Patent Application Publication No. 2-11541. This head carriage device 20 prevents the inclination described above. FIG. 12 and FIG. 13 are a plan view and a side view of the head carriage device 20, respectively.
The head carriage device 20 shown in FIGS. 12 and 13 includes a carriage 21, a head arm 22, a magnetic head 23 mounted on the head arm 22 at an end thereof, and a magnetic head 31 mounted on the carriage 21. A flat spring 24, a fixing member 25, and a torsion spring 27 are disposed opposing the magnetic head 23. Components that have the same function as that of the components of the head carriage device 1 shown in FIGS. 9, 10, and 11 are referred to with the same reference numerals in FIGS. 12 and 13.
In the head carriage device 20, a first protrusion 22b protrudes over the upper face of the flat spring 24 from an end of one of the lateral sides of the head arm 22 along a direction R of the head arm 22, and a second protrusion 25a protrudes over the upper face of the flat spring 24 from the fixing member 25 at the other lateral side, provided with a finger 22a, of the head arm 22. The first and second protrusions 22b and 25a oppose each other in the width direction of the head arm 22.
With this arrangement, as shown in FIG. 12, when the head arm 22 moves in a direction A shown in FIG. 13 while being supported by the lifting mechanism 26 at the finger 22a, the flat spring 24 twists along a line 28 extending between joining parts M and N in a flexible part of the flat spring 24. The line 28 forms an angle xcex8 with a line 30 along the width of the head arm 22, because the joining part M disposed in the vicinity of the first protrusion 22b formed on the head arm 22 is closer to the fixing member 25 than the joining part N disposed in the vicinity of the second protrusion 25a formed on the fixing member 25.
When the torsion spring 27 shown in FIG. 12 is eliminated, the head arm 22 is inclined from the horizontal line H by an angle xcex1, as shown in FIG. 14A, in a manner such that a lateral side 22-2 of the head arm 22 is disposed higher than a lateral side 22-1 thereof which opposes the lateral side 22-2 and which is provided with the finger 22a. 
The head arm 22 provided with the torsion spring 27 at a central part P of the head arm 22, as shown in FIG. 14B, which is the position of the anchoring point 22c, is kept horizontal by the torque D shown in FIG. 11. The torque D is produced by the pressing force of the torsion spring 27 and offsets the inclination in which the lateral side 22-2 is higher than the lateral side 22-1 by angle xcex1.
However, with this arrangement, a problem exists in that the head arm 22 cannot be maintained in a stable horizontal position perpetually. The pressing force of the torsion spring 27 and the lifting force of the flat spring 24 lifting the lateral side 22-2 of the head arm 22 to form angle xcex1 are not always balanced due to variations in the angle xcex1 and the pressing force F (shown in FIG. 11). These variations are caused by variations in the thickness of the flat spring 24, which is within the manufacturing tolerances, and variations in pressing force of the torsion spring 27.
As shown in FIG. 14A, the flexible part of the flat spring 24 comes into contact with the first protrusion 22b having a width L5 and the second protrusion 25a having a width L6 at the joining parts M and N, respectively. Another problem of the head carriage device 20 is that the width L5 and the width L6 are small and large stresses are concentrated thereto when the head arm 22 turns. This reduces the durability of the flat spring 24. The flat spring 24 is plastically deformed and eventually breaks at the joining parts M and N due to the repeated pivoting motion of the head arm 22. This reduces the durability of the head carriage device 20.
In addition, in the head carriage device 20, different stresses are applied depending on the position along the line 28 (see FIG. 12) between the joining parts M and N of the flexible part of the flat spring 24. This prevents the head arm 22 from pivoting smoothly.
Further, in the head carriage device 20, lengths L3 and L4 of the first and second protrusions 22b and 25a, respectively, and the widths L5 and L6 of the first and second protrusions 22b and 25a, respectively, must be designed in the proper shape so that the lifting force applied to the lateral side 22-2 of the head arm 22 is offset by the torque D produced by the pressing force F of the torsion spring 27. The resulting design is complex and difficult. When the specifications of the head carriage device 20 are changed, that is, when the value of the pressing force F of the torsion spring 27 and the thickness of the flat spring 24 are changed, the shapes and the like of the first and second protrusions 22b and 25a must be redesigned, thereby limiting design options.
Accordingly, it is an object of the present invention to provide a head carriage device in which a head arm can be maintained in stably and horizontally when the head arm is pivoted while being supported at one lateral side thereof. Further objectives include improving the durability of a flat spring for a repeated, smooth, pivoting motion of the head arm and providing a simple design having flexible design options.
To this end, according to an aspect of the present invention, a head carriage device comprises a carriage supported to be movable in a radial direction of a floppy disc. A head arm is provided with a magnetic head at an end thereof and a flat spring extends from the other end of the head arm. A fixing member fixes the flat spring to the carriage and overlaps a free end of the flat spring. A resilient member resiliently urges the head arm in a direction in which the head arm moves toward the carriage and a lifting mechanism pivots the head arm both away from and toward the carriage. A finger, to which the lifting mechanism is applied, is provided at one of the lateral sides of the head arm along the radial direction.
In the head carriage device, a first protrusion is provided protruding from an end of the lateral side of the head arm provided with the finger. A second protrusion is provided protruding from an end of the lateral side of the head arm opposing the lateral side provided with the finger. The movement of a free end of the first protrusion away from the carriage is restricted and the movement of a free end of the second protrusion toward the carriage is restricted.
In the head carriage device according to the invention, a restricting finger made of a protruding part of the fixing member may restrict the movement of the free end of the first protrusion. A restricting face provided on the carriage restricts the movement of the free end of the second protrusion.
Additionally, the second protrusion may be made longer than the first protrusion. Each of the free ends may include a curved surface having a predetermined curvature. The free ends may include curved surfaces having substantially the same curvature.